Process for preparing α-olefin polymers and oligomers

ABSTRACT

The invention relates to polymers and oligomers characterized in that they have been prepared from α-olefin monomers or mixtures thereof and the distances between the methyl branching paints are controllable by the selection of the α-olefins and to a process for preparing said novel polymers and oligomers.

This is a continuation of application Ser. No. 055,204, filed May 28,1987, now abandoned, which is a divisional of application Ser. No.827,833, filed Feb. 7, 1986, now U.S. Pat. No. 4,724,273.

The present invention relates to a process for preparing polymers andoligomers of α-olefins having sites of methyl branching at defineddistances which are adjustable due to the selection of the α-olefin.

The polymerization and oligomerization of α-olefins which is known to beachievable by use of a variety of catalysts leads to the formation ofproducts containing 1,2-linkages of the α-olefins. The olefinic carbonatoms form the main chain in the product, while the residue R appears asthe side-chain: ##STR1## Now it has surprisingly been found that it ispossible to link α-olefins with high product yields in a way differentfrom that described above and thereby to produce structural units whichso far have been not known for α-olefin polymers.

According to the present invention, the moiety --CH₂ --R of an α-olefinCH₂ ═CH--CH₂ R successfully has been incorporated in the main chainwhereby methyl side-chains are formed at definite distances depending onthe employed species of α-olefin. Thus, when linear α-olefins areemployed, products are formed which correspond to a 2,ω-linkage.##STR2##

Polymers having such a structure have not been known so far. In theGerman Offenlegungsschrift (DE-OS) 26 23 718 S. Yasui et al. obtain, byhydrogenation of polyisoprene oils, a mixture which allegedly contains70% of a 1,4-polymer having the structure ##STR3## Nothing has beenmentioned on either the residues nor on any evidence of the aboveconfiguration.

In the DE-OS 21 01 069 dal'Asta et al. describe elastomeric hydrocarbonswhich inter alia are obtained by hydrogenation ofpoly-2,3-dimethylbutadiene. Here, as in similar cases of the DE-OS, amixture of cyclic oligomers and linear headtail, head-head and tail-tailoligomers is obtained. The cationic polymerization of 3-methylbutene-lwith AlCl₃ results in the formation of polymers having a probablestructure represented by the formula ##STR4## [I. P. Kennedy et al.,Makromolekulare Chemie 53 (1962), page 28.] All of the mentionedprocesses lead to mixtures comprising polymers part of which has notbeen identified, some of them elastomers, however not to uniformoligomers having the structure shown above.

According to the present invention the distances between the branchingpoints of the methyl groups can be defined as desired by selecting apertinent α-olefin. Thus, upon use of a linear α-olefin having n CH₂groups there are obtained distances amounting to (n+1) CH₂ groups.

The structures of the products obtained in the α-olefin polymerizationaccording to the present invention can be proven of by means of ¹³ C NMRinvestigations. The chemical shifts of the carbon atoms were calculatedfor the respective structures to be expected in accordance with theincrement rules established by L. P. Lindemann and J. Q. Adams [Anal.Chem. 43, 1245 (1971)]. Spectra simulated by using these data togetherwith the corresponding intensities were compared to the Spectra No. 1 to7 as experimentally obtained.

Spectrum No. 1 shows the recorded ¹³ C NMR spectrum of the butene-1polymer. All of the signals obtained in simulation using z=2 (z=numberof the CH₂ groups between the methyl branching points of the polymer)are found in the experimental spectrum. The conformity becomes even moredistinctly evident with increasing chain length of the employedα-olefin.

Due to their defined structures which may be subject to controlledvariations within a wide range, the products offer themselves as modelsubstances for physical investigations. By introducing functional groupsat the sites of the methyl side chains of the product there can beprepared subsequent products bearing regularly distributed functions. Asthe functional groups are spaced apart at precisely defined variabledistances along the main chain, there is a possibility of, e.g.,producing novel regular graft polymers. Furthermore, upon a successiveuse of different α-olefins, block copolymers will become accessiblewhich have different branching distances. The regular structure of thepolymers causes a high thermal lubricant stability to be achieved.

The described new α-olefin polymers are obtainable in high yield byusing a catalyst system which consists of the following components:

a) a Ni(O) compound NiL_(x), wherein the ligand(s) L may be hydrocarboncompounds and/or hydrogen and

b) an aminobis(imino)phosphorane represented by the formula ##STR5##wherein R₁ to R₄ may be same or different and represent n- or iso-alkylgroups, aryl groups and/or trialkylsilyl groups.

The Ni(O) compound preferably comprises unsaturated hydrocarbon ligandssuch as, e.g., ethylene,cyclooctadiene-1,5,cyclooctadecatriene-1,5,9,cyclooctatetraene etc..They may also be produced by reduction of a suitable higher-valentnickel compound in the reaction solution.

The second catalyst component preferably consists of atrimethylsilyl-substituted phosphorane ##STR6##

Since all of the catalyst components are soluble in liquid α-olefinsunder normal conditions, the use of solvents is not required. Ifα-olefins. are used which are solid at the reaction temperature of if ahigher conversion is accomplished and, thereby, the viscosity ismarkedly increased, aromatic solvents are preferred to be used.

The homogeneous catalyst system is generated "in situ", the exact natureof the active compound is unknown. The sequence of the addition of theindividual components and the nature of the employed Ni(O) compound donot exert any influence onto the specific structures of the polymers.The use of the catalyst system on solid support materials is possible.In all variants an atmosphere of a protective gas is required.

The concentration of the Ni(O) compound in the liquid monomer ormonomer/solvent mixture, respectively, is preferably at from 10⁻³ to10⁻¹ mol/l.

The ratio of the Ni(O) compound to aminobis(imino)phosphorane shouldpreferably be at least equimolar; a ratio of from 1:1 to 1:10 isbeneficial. The reaction temperature is from -78° C. to +80° C. andpreferably from -20° C. to +30° C.

Linear and branched α-olefins as well as those substituted by (cyclic)alkyl groups are usable in the polymerization. The number of carbonatoms of usable α-olefins has been checked up to a number of 20. Thisdimension does not restrict the usability of the catalyst system.

Upon use of α-olefin mixtures having any optional composition there areobtained, depending on initial monomers employed, randomly distributedbranching points bearing methyl side chains in the copolymerizationproduct. If during the reaction different α-olefins are successivelyadded to the batch, then block copolymers having differing methylbranching point distributions in the individual blocks are obtained. Thepresence of β-, γ- etc. olefins does not destroy the catalyst systemwhile, however, the activity thereof becomes reduced.

The molar masses and the distribution of molar masses of the productsmay be varied by selecting the reaction parameters such as, e.g., thereaction temperature and reaction time. At temperatures of below about0° C., at molecular weights increasing with a decrease in temperature,narrow molecular weight distributions are obtained. Above or about 0° C.with increasing temperature the molecular weights become increasinglysmaller, while the molecular weight distributions become broader.

The present invention is further illustrated by the followingnon-limiting examples in conjunction with the accompanying drawingswhich are ¹³ C NMR spectra corresponding to the examples as follows:

FIG. 1 is the spectrum of Example 3;

FIG. 2 is the spectrum of Example 2;

FIG. 3 is the spectrum of Example 1; and

FIGS. 4 to 7 are the spectra of Examples 8 to 11, respectively.

EXAMPLE 1

In a glass vessel pre-conditioned by heating under vacuum and filledwith argon 0.69 g of bis(cyclooctadiene-1,5)nickel and 0.92 g ofbis(trimethylsilyl)amino-bis(trimethylsilylimino)phosphorane weredissolved in 40 ml of dry toluene. Upon addition of 20 ml of hexene-1the solution was stirred at 0° C. for 7 hours. In the working-up forproduct recovery the catalyst was decomposed with a methanolic HC1solution, and the product was recovered after precipitation withmethanol. After drying under vacuum there were obtained 10.5 g (78%) ofpoly-2,6-(hexene-1) (M_(n) =1 700): ##STR7##

EXAMPLE 2

In a glass vessel pre-conditioned by heating under vacuum and filledwith argon 0.34 g of cyclooctadectriene-1,5,9)nickel and 0.56 g ofbis(trimethylsilyl)amino-bis(trimethylsilylimino)phosphorane weredissolved in 18 ml of pentene-1, and the solution was stirred at 0° C.for 24 hours. After a working-up procedure as described in Example 1there were obtained 8.4 g (73%) of poly-2,5-(pentene-1) (M_(n) =1 100):##STR8## (This structure conforms to a strictly alternatingethene/propene copolymer!)

EXAMPLE 3

A 100 ml steel autoclave which had been evacuated and filled with argonwas charged with a solution of 0.69 g of bis(cyclooctadiene-1,5)nickeland 0.92 g ofbis(trimethylsilyl)amino-bis(trimethylsilylimino)phosphorane in 30 ml ofdry toluene. Upon addition of 18 g of liquefied butene-1 the mixture wasstirred at room temperature for 3 hours. After a working-up procedure asdescribed in Example 1 there were obtained 11.6 g (66%) ofpoly-2,4-(butene-1) (M_(n) =900): ##STR9##

EXAMPLE 4

In a glass vessel pre-conditioned by heating under vacuum and filledwith argon 0.17 g (0.62 mmol) of bis(cyclooctadiene-1,5)nickel and 0.92g (2.5 mmol) ofbis(trimethylsilyl)amino-bis(trimethylsilylimino)phosphorane weredissolved in 30 ml of pentene-1, and the solution was stirred at 0° C.for 24 hours. After a working-up procedure as described in Example 1there were obtained 17.4 g (91%) of poly-2,5-(pentene-1) (M_(n) =1 300).The structure was in accordance with the product of Example 2. ¹³ C NMRSpectrum No. 2.

EXAMPLE 5

In a glass vessel pre-conditioned by heating under vacuum and filledwith argon 0.34 g (1.24 mmol) of bis(cyclooctadiene-1,5)nickel and 0.46g (1.25 mmol) ofbis(trimethylsilyl)amino-bis(trimethylsilylimino)phosphorane weredissolved in 20 ml of decene-1, and the solution was stirred at 0° C.for 3 hours. Then to the gel-like mass there were added 20 ml ofhexene-1, and the mixture was stirred at 0° C. for another 4 hours.After a working-up procedure as described in Example 1 there wereobtained 24.0 g (85% of the total amount) of a decene-1/hexene-1 blockcopolymer which had a methyl branching point characteristiccorresponding to the molar ratio of the α-olefin reactants (M_(n) =1900).

EXAMPLE 6

In a glass vessel pre-conditioned by heating under vacuum and filledwith argon 0.34 g (1.24 mmol) of bis(cyclooctadiene-1,5)nickel and 0.46g (1.25 mmol) ofbis(trimethylsilyl)amino-bis(trimethylsilylimino)phosphorane weredissolved in 20 ml of dry toluene. Upon addition of 10 ml of4-methylpentene-l the solution was stirred at room temperature for 3hours. After a working-up procedure as described in Example 1 there wereobtained 3.7 g (56%) of poly-2,5-(4-methylpentene-1) (M_(n) =800):##STR10##

EXAMPLE 7

In a glass vessel pre-conditioned by heating under vacuum and filledwith argon 0.34 g of bis(cyclooctadiene-1,5)nickel and 0.46 g ofbis(trimethylsilyl)amino-bis(trimethylsilylimino)phosphorane weredissolved in 20 ml of dry toluene, and upon addition of 7.0 g ofeicosene-1 the solution was stirred at room temperature for 14 days.After a working-up procedure as described in Example 1 there wereobtained 2.4 g (34%) of poly-2,20-(eicosene-1) (M_(n) =1 200).

EXAMPLES 8 to 11

Heptene-1, octene-1, nonene-1 and decene-1 were reacted using theprocedures of the Examples as indicated in the following Table whichalso shows the obtained yields and M_(n) values.

                  TABLE                                                           ______________________________________                                        α-Olefin Polymerization:                                                           according tempera-   yield                                         α-olefin                                                                           to Example                                                                              ture (°C.)                                                                        (%)  M.sub.n                                  ______________________________________                                        Heptene-1  4          0         66   1 200                                    Octene-1   2          0         67   1 300                                    Nonene-1   4         25         32   1 000                                    Decene-1   1         25         27   1 300                                    ______________________________________                                    

The ¹³ C NMR Spectra Nos. 4 to 7 were measured using respective productsamples.

What is claimed is:
 1. A polymer or oligomer prepared from an α-olefinmonomer having more than 3 carbon atoms, or mixtures thereof, thedistances of the methyl branching sites being controlled by theselection of the α-olefins, and consisting of units having the structure##STR11## wherein R═H and/or alkyl, and n═1-17.
 2. A polymer or oligomeraccording to claim 1, wherein the α-olefin is linear or branched,unsubstituted or substituted with (cyclic alkyl groups, and has 4 to 20carbon atoms.
 3. A polymer or oligomer according to claim 1, wherein nis
 1. 4. A polymer or oligomer according to claim 1, wherein n is 3-17.5. A polymer or oligomer according to claim 1, wherein the α-olefin islinear or branched, unsubstituted or substituted with (cyclic alkylgroups, and has 4 carbon atoms.
 6. A polymer or oligomer according toclaim 1, wherein the α-olefin is linear or branched, unsubstituted orsubstituted with (cyclic) alkyl groups, and has 6 carbon atoms.